Two main rounds of thunderstorms will likely impact southern/eastern Ontario Tuesday and again on Wednesday as a series of disturbances ride along a boundary dividing the hot and humid air to the south from the cooler, less humid air to the north.
Exact timing and intensity of these thunderstorms is difficult to pinpoint, but there is the chance that parts of these regions, especially southwestern Ontario, could be in store for some severe thunderstorms during the period.
The first map below shows the area with the best chance of thunderstorms for Tuesday/Tuesday night...
By Wednesday, high pressure over the southern U.S. will allow the heat and humidity to build over the Ohio Valley and Middle Atlantic region, which will further fuel the storms forming along the northern rim of the high pressure ridge to the north.
A backdoor front will bring drier and cooler air in from the northeast Thursday and Friday, especially to areas north and east of the GTA.
Heavy rainfall and flooding potential for southern Alberta through Tuesday night.....
A slow-moving, upper level storm system will be the primary cause for locally heavy rainfall over extreme southern Alberta through Tuesday night and perhaps into southwestern Saskatchewan.
Rain and embedded thunderstorms could cause some flooding in southern Alberta during the period, especially south of Calgary. Rainfall totals will likely average in the 20-50 mm range with some isolated higher amounts possible.
Wednesday will remain unsettled in southern Alberta, but the heaviest rainfall and thunderstorms will likely shift into Saskatchewan.
I will be out of the office the rest of this week, but will be back for next week.
Latest model update points toward a soggy southern U.S. and a return to the western Canada warmth.
How did snow cover extent fare this past winter across Canada and a look back at the Great Ice season.
An update on the long range and a look at the overall pattern the rest of this week in Canada.
This is my latest interpretation of the ECMWF forecast model that now goes out through the middle of May.
What the summer weather pattern might look like under a moderate to strong El Nino.
Weekly long-range forecast model update and a look back at March.